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  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
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  <script>
    //1.声明一个年龄的变量
    let age; //var 不再使用了

    //2.赋值
    age = 21;
    //3.打印
    console.log(age);

    //变量直接初始化
    let age1 = 21;


  </script>
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